The mophie juice pack line of rechargeable external batteries for the iPod and iPhone is growing. In addition to the juice pack air line of protective cases with built-in battery, there's also two clever battery packs with retractable iPod connector, the juice pack reserve and the juice pack boost.
The mophie juice pack reserve is a small and light 1000mAh handheld charger (3.15 x 1.60 x 0.63 in.) for $39.95, while the juice pack boost packs 1500 mAh in a slightly larger size (3.70 in x 2.03 in x 0.63 in.) for $59.95. Both are powered with a high-output lithium polymer battery rated to charge up to twice as fast as conventional 500mAh batteries.
You charge these through a micro USB port on the side, and then slide out the retractable 30-pin iPod connector to charge your iPod or iPhone. There's no power button to accidentally leave on -- it turns power on only when it is connected.
The juice packs have a handy set of four LEDs to indicate charging status, or you can press the button to have the light up to show the charge level, so you know when it's time to recharge.
And if the juice pack design was not clever enough, holding down the button turns on a built-in LED flashlight.
See my Portable Power Accessories Gallery for more on portable chargers
Find the mophie juice pack reserve
and juice pack boost on Amazon.com